Forming pad for hydraulic press



Feb. 4, 1964 P. o. PFEIFFER ETAL FORMING PAD FOR HYDRAULIC PRESS 5 Sheets-Sheet l Original Filed Feb Feb. 4, 1964 P. o. PFEIFFER ETAL 351205205 FORMING PAD FOR HYDRAULIC PRESS Original Filed Feb. 7, 1956 5 Sheets-Sheet 2 INVENTORS v Paul 0. Pf'eif'fer Charles 0. Slemmons 52kg?, am www ATTORNEYS Feb. 4, 1964 P. o. PFEIFFER ErAL FORMING PAD FOR HYDRAULIC PRESS Original Filed Feb. 7, 1956 5 Sheets-Sheet 3 zu /o INVENTORS S nm n .um m I O 54mm ad@ s di, ar f ms Feb. 4, 1964 FORMING PAD FOR HYDRAULIC PRESS Original Filed Feb. '7, 1956 o. PFEIFFER ETAL 3,120,205

5 Sheets-Sheet 4 elli" 55 FTJE INVENToRs Paul 0. Pfeiffer Charles nslemmfons fwn/wwwa@ ATTORNEYS Feb. 4, 1964 P. O. PFEIF'FER ETAL FORMING PAD FOR HYDRAULIC PRESS Original Filed Feb. '7, 1956 Y 5 Sheets-Sheet 5 20 F17. En

INVENTORS Paul 0. Pfeiffer Charles 0. Slemnwns ATTORNEYS United States Patent O amazes roar/rw o ran ron rrrnnanrre Paul Pi lier, Cuyahoa Fells, and @harias lem mons, Alu-an; Ghia; asux -rs to The General Tire and The present invention relates to an improved hydraulic ress and more particularly to a press of simple inexpensive design constructed so that the rubber parts thereof function efhciently and have a maximum useful life.

According to the invention, an elastic rubber forming pad is provided which is bonded to a rigid rim member and gradually reduced in thickness near the lim member to facilitate flexing of the pad and to prevent rupturing of the bond between the pad and the rim member. The rim member is held against movement relative to the press frame so that the marginal edge of the forming pad does not move during operation of the press. if desired, the elastic rubber pad and its rigid rim member may be made symmetrical about its horizontal medial plane so as to be reversible. However, non-symmetrical constructions may `also provide long pad life particularly where rubber throw pads or other protective layers are used between the forming pad and the article being formed so as to protect the pad from cutting or excessive abrasion.

A thin rubber diaphragm is employed above the forming pad to provide an expansible pressure chamber for receiving hydraulic iiuid under pressure. When the iluid is under high pressure during forming of articles in the press, there is a tendency to extrude the rubber of the forming pad and fthe diaphragm through any small openings between metal parts of the press. The press shown herein is designed to prevent extrusion of the rubber diaphragm and to reduce damage to the forming pad due to changes in its shape during the forming operations.

Strips of metal with rubber attached thereto are preferably employed at the margin of the article-receiving space below the rubber forming pad to limit the downward movement of the pad near said margin and to reduce stresses on the pad.

rIhe forming pad will last for long periods of time without the use of rubber throw pads or facings of abrasion-resistant rubber to protect the pad. However, the pad will usually last several times as long when throw pads are used so that the pad does not contact the articles being formed and is not cut or otherwise damaged substantially by the articles.

An object of the invention is to provide a hydraulic press of simple construction which is easy to assemble and disassemble and which will operate for a maximum period of time without replacement of the rubber parts thereof.

A further object of the invention is to provide a simple and inexpensive forming pad assembly for a hydraulic press which is durable and which functions effectively for long periods of time.

A still further object of the invention is to prevent rupturing of the bond between the rubber lforming pad and the rigid rim member therefor.

Another object of the invention is to minimize stretching of the rubber diaphragm and the rubber forming pad during operation `of the press.

Other objects, uses and advantages or the invention will become apparent to those skilled in the art from the following description and claims and from the drawings in which:

,. lCC

FloURE 1 is a fragmentary end elevational View of the hydraulic press of the present invention on a reduced scale with par-ts omitted and parts broken away and shown in section;

FGURE 2 is a fragmentary longitudinal vertical sectional vieW with parts broken away and with parts omitted taken substantially on the line 2-2 of FlG. l;

FiGURE 3 is a fragmentary transverse vertical sectional View of the press shown in FlG. 1 on a larger scale;

FlGURE 4 is atop plan view on a reduced scale showing the rubber diaphragm;

FGURE 5 is a side elevational view off the diaphragm shown in FlG. 4 and on the same scale;

FGURE 6 is a fragmentary vertical sectional view taken on the line 6 6 of FlG. 5 and on a larger scale;

FIGURE 7 is a top plan view on a reduced scale of the rubber forming pad of the present invention;

TFlGURE 8 is a side elevational View of the pad shown in FIG. 7 on the same scale;

FIGURE 9 is a fragmentary vertical sectional view taken on the line Q-Sl of .the FlG. 8 and on a larger scale;

FGURE 1() is a fragmentary vertical sectional View of the press on the same reduced scale as FlG. 9 showing the parts in their retracted positions when no pressure is applied to the forming pad;

FEGURE 11 is a fragmentary transverse vertical sectional view on a reduced scale with parts broken away showing an improved form of press according to the present invention, the parts being shown in their positions when no pressure is applied to the press;

FIGURE l2 is a fragmentary transverse vertical sectional view of the press shown in FIG. l1 on the same scale showing the position of the parts when the press is subjected to normal operating pressure and the rubber parts are compressed during forming of articles in the press;

FGURE 13 is a fragmentary longitudinal Vertical sectional view similar to HG. 12 and on the same scale showing the position of the parts when the press is subjected to normal operating pressure;

FGURE 14 is a top plan view of the press on a reduced scale with parts omitted;

FGURE 15 is a top plan view `on a reduced scale of the diaphragm employed in the press of FIGS. 11 to 14;

FIGURE 16 is a fragmentary longitudinal vertical seetional View taken on the line 'i6-lo of HG. 15 and on a larger scale;

FlGURE 17 is a top plan view on a reduced scale of the resilient deformable forming pad employed on the press of FiGS. 1l to 14 and its rigid rim member;

FEGURE 18 is a fragmentary longitudinal vertical sectional view taken on lthe line 113-18 of FIG. 17 and on the same scale as PEG. 16;

FlGURE 19 is a fragmentary top plan View on a reduced scale of the sealing gasket employed on the press of FIGS. 11 to 14 with parts broken away; and

FIGURE 20 is a fragmentary vertical sectional view of the ygasket tallen on the line 2d-20 of FIG. 19 and on a larger scale.

Referring more particularly to the drawings in which the parts are identied by the same numerals throughout the several views, FlGS. l and 2 show a high-pressure hydraulic press having an outer laminated coniining ring 1 made up of a ser'es of concentric metal cylinders and upper and lower flat vertical end plates 2 and 3 located at opposite ends of the press and bolted or otherwise rigidly com' :ted to the opposite ends of the ring l. A circular hole 4 may be provided in each plate 2 at each side of the press to facilitate lifting and moving of the press. The press ring 1 is accurately machined and ground to provide 3 an internal cylindrical surface which extends between the end plates 2.

Rigid upper and lower metal ller blocks 6 and 7 are mounted within the press cylinder l with their flat vertical end faces engaging the flat surfaces of the end plates 2 and 3. The ller blocks are provided t ith external semicylindrical surfaces with the same radius as the surface 5 as best shown in FIG. l so as to engage the latter surface throughout the width of the `filler blocks when pressure is applied to the work. The lower surface of the block 6 is horizontal and parallel to the flat upper surface of the block 7, and the side portions of the blocks are notched to provide ways or steps which in the assembled machine receive the parallel longitudinal portions 3 of the endless hollow rectangular pad-retainer ring or block 9 and for preventing radial movement of said longitudinal portions relative to the press cylinder 1. The portions S have semi-cylindrical surfaces of the same radius as the sur-face 5 of the press cylinder so as to conform to said surface.

rllhe ends of the portions 8 extend beyond the ends of the blocks 6 and 7 and are integrally joined Eby thick transverse portions 5l of rectangular cross section having a height less than that of the portions 8 so as to provide an endless structure having sufficient strength to withstand the high pressures within the press (which can stretch the portions 8 more than one-sixteenth of an inch longitudinally). The portions S are provided with notches 52 near their opposite ends to receive the vertical end plates 2 as best shown in FIG. 2.

The transverse portions 5l `of the rectangular metal block 9 project a short distance inwardly between the filler blocks 6 and 7 and have flat vertical faces 10 which are parallel to the ilat vertical faces of the plates Z and 3. The horizontal upper faces of the portions El are located in a first plane a short distance below the lower horizontal surface of the iiller block 6 and the ilat horizontal bottom surfaces of the portions 5l are located in a second plane that is spaced from the horizontd upper surface of the block 7 to provide room for a rigid rectangular horizontal metal filler block 1l.

The block 11 has'a hat bottom surface that rests on the lower block 7 and has a dat horizontal upper surface that extends the length of the block 7 `and that is spaced below the portion 51 to provide room for a hat rigid horizontal metal press table 12 which as shown herein extends beyond the ends of the longitudinal portions 8 of the padretainer ring 9. The upper edges of the lower plates 3 are just below the upper surface of the -filler block 1l so as to permit sliding of the block longitudinally into and out of the press.

As shown in FIGS. l and 2, the horizontal bottom and top surfaces of the filler blocks 6 and lll, respectively, and the flat vertical inner surfaces of the longitudinal portions S and the transverse portions 51 ydefine a chamber or receptacle of rectangular longitudinalV amd transverse vertical cross section. A pressure pad assembly is mounted in said chamber including an upper rigid metal plate 13, a rigid endless rectangular metal pad-support ring i4 of tapered cross section, a rigid steel rim member l5 resting on the pad support ring ld below the marginal portion of the plate i3, an elastic rubber sealing gasket 53 resting on the rim member, a thick elastic rubber forming pad i6 vulcanized to the rim member throughout its circumference, an elastic mubber diaphragm or inflation bag 17 above the pad, a flat horizontal rigid metal plate 18 for clamping the marginal portions of the diaphragm against the plate 13, and a pair of horizontal longitudinal spacer bars 49 for supporting the pad support ring le.

In view of the large size of the rubber parts and the high pressures involved in a 20,000 ton direct-acting press of the type shown herein during the forming of aluminum and steel parts, the design of the forming pad assembly is very important. It is particularly important to prevent rupturing of the bond between the rim member l5 and the rubber forming pad and to provide a pad having a long useful life.. r[lhe press of the present invention is constructed so that the pressure pad assembly will last for a maximum period of time without replacement of arts. p rThe rectangular pad-support ring 14 is of uniform cross section through its circumference yand extends the full length and width of the rectangular chamber so as to provide a rigid stationary support for the pad rim member l5 that extends throughout the periphery of the forming pad le. The spacer bars 49 rest upon elevated guide portions 5? of the lower block 7 that engage the opposite sides of lthe filler block ll md have horizontal upper surfaces that engage the hat bottom surfaces of the pad-sup-` po1t ring id to support said ring.

The pad-support ring has a horizontal notch or ledge of a size to receive the pad rim member l5 and has rounded top portions l@ that project upwardly a short distance above the bottom edge of the member l5. The ring i4, as shown herein, also has a tapered pyramidoidal inner surface tangent to the arcuately curved surfaces of the top portions i9 and that extends from said top portions to the flat bottom surface of the pad-support ring. When the press is in operation, the pad-support ring i4 engages the hat upper lsurfaces of the press table i2, said table being supported by the filler block lil and the soft metal wearing strips Ztl and 2l above and below said fiiler block.

The rectangular portion of the press table @12 inwardly of the pad-support ring 14 is thicker than the marginal portions of the table and has a flat horizontal upper surface 22 that is normally above the bottom surfaces of the pad support ring and that extends the full distance betwen the parallel portions of said pad-support ring. The thickened portion of the metal press table, therefore, provides shoulders which t within the pad support ring l's to prevent horizontal movement of the table during the forming of articles and which may readily be moved below the pad-support ring when the table is removed.

As shown in FIGURE 2, there is a generally pyramidoidal chamber 23 formed within the pad-support ring 14 and between the bottom surfaces of the forming pad 16 and the upper surface of the press table l2. This chamber is large enough `to receive a plurality of sheet meta-l :articles to be formed together with `a plurality of dies and throw pads.

A rectangular elastic rubber vfiller ring 54 of normally square cross section extends throughout the periphery of the rectangular plaid support ring t4 as shown in FlGS. 1 to 3, the outer vertical faces of the rubber ring 54 being contiguous to the pad support ring. The rubber ning isV mounted on an endless rectangular sealing strip 55 of spring steel or other suitable sheet metal which is rigidly connected to the table 12 by la series of screws 6l and which extends throughout the periphery of the ring 14. The metal sealing strip is of substantial-ly uniform cross section throughout its periphery and has an outer vertical ftange 56 yadjacent the inner surface of the ring 14 and an inner ange 57 that is fbent outwardly toward the ring 14 lto grip the rubber ring 54. The rubber ring is provided lwith a tapered peripheral groove 58 for receiving the inner metal flange.

A rubber throw pad may be mounted above the articles being formed in the press to extend the useful life of the forming pad E6. However, the press will {function effectively even when such throw pads are omitted as in 'Fl-G. 3.

When it is desired to `slide the press table l2 out of the press, the filler block l is slid longitudinally from :between said table and the lower block '7, being guided by the bars 49 and the raised portion 5? so that the table and the articles Ithereon may be dropped below the pad sup port ring 14. With the block 11 removed there is suihcient space between the block 7 and the pad retainer ring 9 to pernnt sliding of the press tabie :L2 and theY rubber ring $4 and the dies thereon Ilongitudinaliy to remove the shaped articles from the press and to insert new articles into the press. After the press table is returned to its original position, the filler block 11 is replaced.

'll-he upper plate 13 has a marginal portion of increased thickness that is of substantially uniform cross section throughout its periphery. Said marginal portion is shaped to provide a rounded peripheral shoulder 26 that is coettensive with the pad rim member l5, the arcuatel-y curved surface of said shoulder being tangent to the dat horizontal bottom surface of the upper plate 13 so as to provide a smoothly curved surface for engaging the diaphragm 17 and a flat surface for enga ig the clamping plate 18. The marginal edge portion of said diaphragm extends between the plates 13 and 18 and is held in a iixed position lagainst the plate 13 by the plate l which is held against the upper plate by means off screws 27 or the like.

The pad rirn member 15 is ysecurely held a xed position by the upper plate i3, the seal-ing gasket 53 and the pad support ring 14. The sealing gasket is normally compressed between the upper plate and the pad Irim member so as to press said rim member down lagainst said pad support ring. The volume of rubber in the sealing gasket is sufficient to fill the space between the pad rim member @d the marginal portion of the plate 13 when the rubber forming pad is subjected to maximum pressure as shown in FlG. 3.

At least one metal strip is provided on the sealing gasket to prevent extrusion of the rubber of the gasket between the metal parts. As herein shown, the endless gasket 53 is provided ywith upper metal strips 59 that extend iat its upper edge substantially throughout the peripery of the gasket 53 and at its lower edge with lower met-al strips 6i? of similar extent, the cross section of the gasket being generally as shown in FIG. l0, which is drawn substantidly to scale.

The pad rim member l5 may be made of various strong inextensible materials and may be sectional, but is preferably formed as an endless ring or band of steel or other strong rigid lmetal which may be electively bonded -to rubber. The forming pad 16 may have a thickness throughout the maior portion of its length and width not substantially less than the axial height of the rim member l5 and is preferably vulcanized to the rim member for an axial distance at least about equal to said thickness. As herein shown, the rectangular rforming pad is made of la homogeneous elastic rubber and is vulcanized to the rim member throughout its periphery, the bond between the member and the rubber having an axial width throughout the periphery of the pad not substantially less than the thickness of the central or interior portion of the pad. Said pad lmay have a thickness at its outer edge not substantially less than the avenage thickness of said interior portion. i

The rim member 15 and the pressure pad 16 are best shown in FB2-S. 7 to 9. The pad rim member may be split or sectional but is preferably endless and made of a strong rigid material, such as steel or other metal, which may be vulcanized to rubber to provide a strong bond. As herein shown, the rim member l5 has upper and lower edges located in planes located equal distances `from the medial plane of the pressure pad and so that the pressure pad may be reversed and used in the upside-down position. Portions of the rim member are arcuatelly curved to provide rounded shoulders 23 and to insure that the rubber will not separate from the rim member a-t the corners.

The forming pad le is made of an elastic rubber-like material which may be deformed under high pressure to cause the sheet metal blank to conform to the shape of its die 2d. The material is preferably a durable flexible incompressible elastic rubber which provides a deformable homogeneous pad. Excellent results may be obtained where the vulcanized pad l consists of a homogeneous elastic tread rubber with a durometer hardness of about 6() to 70, but rubber of low durometer hardness may be used particularly where a throw pad or a facing layer is interposed between the forming pad and the article Ibeing formed to reduce damage to the pad.

vIt is preferable to employ elastic rubber throw pads to cover the articles being formed in the press and to prottect the forming pad against cutting and excessive abrasion since they substantially increase the lite of the forining pad and are readily replaceable when they are worn out. The throw pads may be made of a highly flexible insulating material such as silicone rubber where the articles are at elevated temperatures so as to protect the forming pad from the damaging effect of the heat. The pad may lalso be provided with a facing of silicone rubber but throw pads are usually preferred.

The rubber forming pad le is vulcanized to the rigid rim member 15 throughout its periphery to provide a strong bond of maximurn area. Before vulcanization the peripheral edge surface of the forming pad may be coated with a suitable rubber-to-metal adhesive in the conventional manner so that an edective bond will be provided. Conventional brass plating may be employed or other conventional methods may be used to obtain a bond of. maximum strength. In the press shown in FlGS. 1 to 3, the peripheral edge surface of the forming pad has a uniform width throughout its periphery in the neighborhood of about six inches and is vulcanized to the rim member 1S throughout its area.

The forming pad 16 may have diiierent sizes and shapes while obtaining the benefit of the present invention. A circular pad is durable and will function eiliciently, but it is preferable to employ a generally rectangular pad in a press of the character described herein that is constructed for easy assembly and disassembly. The forming pad preferably has a length of about 8 to l2 feet, a width of about 3 to 6 feet, an average thickness of about 4 to 8 inches, and a minimum thickness in the neighborhood of about 3 inches.

The marginal portion Z9 of the pad is necked down and reduced in thickness throughout the periphery of the pad to provide a marginal recess 36 with a maximum depth of at least one-half an inch or so which gradually decreases in depth toward the rim member 15. The minimum thickness of the marginal portion 29 is preferably about 20 to 40 percent less than the average thickness of the pad and/ or the thickness of the central portion 31 of the pad so as to facilitate llexing of said marginal portion during operation of the press and to avoid rupturing of the bond between the pad 16 and the rim member 15.

It will be apparent that the rubber forming pad may be of various shapes and sizes particularly where the pad is unsymmetrical. As herein shown, the pad 16 in its normal unstressed condition as shown in FIG. 9 is symmetrical about its horizontal medial plane, two endless marginal recesses Sil and two endless projecting peripheral portions 32 of the same size being provided. A symmetrica] pad has the advantage that it may be turned upside down or reversed to obtain a maximum useful life from the pad.

As herein shown, the central portion 31 of the pad 16 has a uniform thickness of six inches to provide flat upper and lower faces 33 of substantially rectangular form that are parallel to the edges of the rim member 15 and that extend to within about live inches of the rim member on each side thereof. The marginal portion 29 has a vertical cross section throughout the periphery of the forming pad which may be the same as shown in FIG. 9. The pad gradually decreases in thickness outwardly of the central portion 31 to provide smoothly curved tapering surfaces 34 tangent to the horizontal surfaces 33 and the horizontal bottom surfaces 35 of the marginal grooves 3l). As herein shown, the minimum thickness of the pad and the distance between the surface 35 is about four inches, but it will be apparent that the size of the pad may vary considerably even when the pad is symmetri- Y cal.

The pad gradually increases in thickness outwardly of the surfaces 35 to Vform the endless peripheral portions 32 which have arcuately curved surfaces 36 tangent to the surfaces 35. As shown in FIG. 9, the surfaces 36 have a constant radius of curvature and are almost tangent to the inner vertical surface of the rim member 15. The surfaces 34, 35 and 36 define the bottom and side Walls of the peripheral recesses 30 and extended horizontally a short distance from the rim member to the iiat surface 33. This distance is preferably less than onethird the Width of the forming pad and may be as small as five inches in a symmetrical pad of the type shown in FIG. 9.

Means is provided in the press of the present invention for forming an'expansible iiuid-tight chamber above the forming pad 16 to apply high pressure to the pad. Although a tubeless construction is possible, such means preferably includes an inflatable bag or tube of iiexible elastic rubber-like material or a rubber-like diaphragm. Hydraulic fluid under a high pressure (for example, 5,000 to 6,500 pounds perV square inch) may be supplied to the expansible chamber in a suitable manner to eifect operation of the press. As herein shown, the upper half-moon iiller block 6 is provided with a longitudinal cylindrical bore 37 to receive an elbow 38 and a horizontal uid supply pipe 39 which extends through a slot 40 in the plate 2 to a suitable source of hydraulic fluid under high pressure. The block 6 is also provided with a vertical cylindrical bore 41 to receive a vertical pipe 42 that is connected to the elbow 38, said pipe having a circular ange 43 that engages the bottom of the block 6 to limit upward movement of the pipe and the elbow. The flange has a tight fit in a circular opening in the plate 13, and the lower end portion of the pipe has a close fit in a circular opening in the plate 18 as shown in FIG. 3 so that there is no substantial leakage around the inlet fitting.

The diaphragm 17 is molded as a single piece of flexible and extensible elastic homogeneous rubber having marginal portions which may be clamped between metal members to seal the chamber formed by the diaphragm and the metal parts of the press. Like the pad 16, the diaphragm 17 is preferably generally rectangular and preferably has a width of about three to six feet and a length of about eight to twelve feet; but, unlike the pad, the average thickness of the diaphragm is preferably not in excess of about five-eighths of an inch. It will be apparent that the thickness of the diaphragm may vary considerably and that said thickness may be increased toward the margins of the diaphragm. The diaphragm 17 shown in FIGS. 4 to 6 has a substantially uniform thickness in the normal unstressed condition of about three-eighths of an inch. The marginal portion of the diaphragm has a uniform vertical cross section throughout its periphery Y which may be the same as shown in FIG. 6. As shown herein, the rubber diaphragm is molded with a horizontal rectangular bottom wall 4S of uniform thickness which integrally joins the marginal portion 44 within one or two inches of the outer periphery of the diaphragm and with an inturned marginal portion which provides a peripheral side wall 46 of rounded cross section and uniform thickness. The side wall 46 is integrally joined to Vthe peripheral portion 44 and has a marginal Vertical edge 47 of substantially rectangular form for insertion between the upper plate 13 and the marginal portion of the vclamping plate 18. When the diaphragm is in position in thepress and is subjected to hydraulic iiuid under high pressure, the wall 46 conforms to the shape of the rounded concave shoulder 26 of the plate 13 and the central portion 45 conforms to the shape of the underlying central portion 31 of the forming pad. The sealing gasket 53' completely fills the space between the marginal portion 26 of the plate 13 and the pad rim member 15 to prevent pinching of the diaphragm by the metal parts vso that the diaphragm has a maximum useful life. The life of the diaphragm may be further extended due to the design of the top surface of the forming pad.

normal unstressed condition as shown in FIGS. 1 and 2 l so that stretching of the rubber wall 45 is minimized during forming of articles in the press.

Any suitable hydraulic uid which does not damage the diaphragm 17 may be employed in the pressure chamber above the pad 16. Such iluid may be a hydraulic oil, in which case 'the rubber for the diaphragm is an oilresistant -type which is not damaged by such oil.

FIGURES l1 to 20 show details of construction of a modified form of hydraulic press according to the present invention which is identical to the press of FIGS. l to 3 except that the forming pad assembly within the retainer flation bag 17a above the pad, and a dat horizontal rigid metal plate 18a for clamping the marginal portions of the diaphragm against the plate 13. FGURES 11 to 13 are drawn substantially to scale so that the size of the parts 'and their operation will be apparent upon inspection.

The rectangular pad support ring 14a is of uniform cross-section throughout its periphery and ts against the inner sur-faces of the pad retainer ring S, being supported by the spacer bars 49. The rings has a rounded upper surface y63 for engaging the forming pad 16a and flat vertical inner faces 64 tangent to the surface 63. The surfaces 64 are parallel to and spaced a short distance from the iiat vertical outer faces of the rubber ii'ller ring 54 ias shown in FIG. 1l throughout the inner periphery of the rectangular ring 14a so as to provide a narrow clearance space 65 to permit insertion and removal of the table 12 and the rubber ring 54 attached thereto. The flange 56 of the spring metal strip 55 has a height greater than the width of said clearance space and engages the pad support ring 14a during the application of high pressure as shown in FIG. 12 so as to prevent extrusion of rubber between the table 12 and the ring 14a into the space 66 above the, wear strip 67. The height of the flange 56 is substantially greater than the maximum clearance between the table 12 and the ring 14a so that the rubber cannot extrude between these parts even if the pad retainer ring 9 were to stretch as much as one-tenth of an inch longitudinally.

It IWill be noted that a clearance 63 exists between the end portions 51 of the ring 9 and the ends of the plate 13a when high pressure is applied to the press as indicated in FIG. 13 due to longitudinal stretching of the side portions .8 of said ring, but that no substantial clearance exists between the plate '13a and the side portions 8 (seevFIG. 12) due to the relatively small radial expansion of the press cylinder 1 under the same pressure. At zero pressure, of course, there is no clearance and the plate 13a and the overlying iil'ler block 6 engages the ring 9 throughout its inner periphery as indicated by FIG. l1.

The outer portion of the pad support ring 14a is shaped the same as the ring 14 and is provided with a peripheral lledge for supporting the pad rim member 15a, said pad support ring having the same vertical cross section throughout its periphery. The ledge has a flat horizontal surface 69 with a width corresponding to that of the narrow lower portion 60 of the rim member 15a. The pad support ring 14a also has a vertical surface It will be .noted that the bottom surface of the diaphragm 17 is held ,in a concave position when the forming pad 16 is in its 71 tangent to the curved surfaces 63 and engaging the inner vertical surface 72 of the rim member 15a. The vertical outer surface 73 of the ring 14a engages the retainer ring 9 throughout its height and periphery.

'he outer vertical surface 74 of the pad rim member 15a also engages the ring 9 throughout its periphery. As herein shown, the ring 9 and the press cylinder 1 are provided with a series of aligned openings 75 and 76 to receive a series of long studs '77 spaced around the pe- `riphery of the rim member 15a. The rim member is provided with a series of internally threaded openings 7 S to receive the externally threaded inner end portions of the studs, and nuts 79 may be screwed onto the externally threaded outer end portions of the studs. The rim member 15a has a thickened upper portion @il containing the holes 7S and has a uniform cross section throughout its circumference as shown in HG. 18 which is drawn to scale. The upper surface of the rim member comprises a sloping portion Si and a llat horizontal portion 82.

The elastic rubber forming pad `16a is made of the same material as the pad le and has substantially the same external dimensions. The pad 16a preferably has a length of about 8 to l2 feet, a width of about 3 to 6 feet, an average thickness of about 4 to 8 inches, and a minimum thickness greater than three inches. Said pad is vulcanized throughout its circumference to the rim member lSzz and is reduced in thickness near its margin like the pad 16. However, the pad 16a is not symmetrical. The rectangular central portion 82 of the pad normally has a uniform thickness not substantially greater than the height of the rim member 15a and extends more than one-third the width and more than two-thirds the length of the pad. The pad has a marginal groove in its upper face with a normally pyramidoidal surface 83, a normally flat horizontal surface 534 that extends throughout the periphery of the pad, and a rounded marginal surface 85. lThe bottom surface 86 of the pad 16a is normally horizontal and dat to Within a few inches of the marginal edge of the pad as shown in FIG. l1 which is drawn substantially to scale. lt will be apparent that the outer portion of the rubber pad normally has substantially the same cross-section throughout as shown iti lul-GS. 11 and 18. The bottom part of the forming pad i512 is provided with a marginal groove `having a rounded surface S7 that conforms to the shape of the rounded surface 63 of the pad support ring, whereby the marginal portion 3S of the pad has a thickness less than that of the outer portion S9.

The intermediate outer portion 89 preferably has a thickness to 25 percent less than the central portion 82 and the marginal portion $8 preferably has a minimum thickness that is 2O to 40 percent less than that of said central portion. However, the area of the bond between the rim member o and the marginal edge surface or face of the pad 16a preferably has a substantially uniform vertical height Lthroughout the periphery of the pad greater than the thickness of the outer portion 89' and not substantially less than the average thickness of the pad. As herein shown, said bond area has a height not substantially less than that of the central portion S2, the outer portion S2 has a thickness about one-sixth less than that of said central portion, and the marginal portion 83 has a minimum thickness about one-third less than that of said central portion.

In the press shown herein the pad 16a has a length of about 10 feet and a width of a little over 4 feet and the central portion 8?. of the pad has a thickness of six inches, but it will be apparent that the sizeof the pad may vary considerably.

The forming pad 16a is completely covered by the thin homogeneous impervious elastic rubber inflation bag or diaphragm i711. As shown herein, said diaphragm comprises a main central body portion 953 of normally uniform thickness and substantially rectangular shape, an upstanding marginal portion 91 having a uniform thickness greater than that of said body portion and having an internal horizontal flange 92, and an outer portion 93 integrally connecting the portions l9G and 91 and gradually increasing in thickness in lan outward direction.

FIGURES l5 and 16 show the diaphragm in its normal unstressed condition, the portion 93 being bowed as shown in FIG. 16 throughout the periphery of the diaphragm due to the fact that the part of the diaphragm within the vertical marginal portion 91 has a surface with a length and width substantially greater than the length and width of the portion The length and width of the diaphragm 17a may be the same as that of the pad 16a but the average thickness of the diaphragm is only a small fraction of the thickness of said pad and is preferably less than ve-eighths of an inch. The central body portion 99 of the diaphragm preferably has a thickness of about one-quarter to one-half of an inch and the outer portions 91 and 13 preferably have an average thickness not substantially in excess of about three-fourths of an inch.

The marginal portion of the upper plate 13a is formed to provide a vertical llange 94 wln'ch has a uniform vertical cross section throughout the periphery of the plate as shown in FiGS. ll to 13. The flange 94 is shaped the same as the upper portion of the rim member 15a and has the same thickness as is apparent from the drawings, the lower surface of said ange having tapered and dat surfaces corresponding in size and shape to the surfaces 81 and S2 of the rim member.

The iiat metal clamping plate 1an extends to within a fraction of an inch of tue flange 945 and is held against the ilat bottom surface of the plate 13a by a series of screws 95, the marginal portion 96 of the clamping plate being spaced from said flat bottom surface a distance substantially less than the normal thickness of the elastic rubber ilange 92 of the diaphnagm so that said rubber ange is compressed to form an air-tight seal at the margin or the diaphragm. As herein shown, the rubber iiange g2 :is compressed throughout the periphery of the diaphragm to about two-thirds its original thickness by the clamping plate so that no lluid can leak from the high pressure chamber above the pad 16a during the forming of articles 1in the press.

Due to the bulge -in the outer portion 93 of the unstressed diaphragm 17a, the portions 9d and 93 of said diaphragm which engage the top of the pad `16a have a .irface area at least as great as that of the top surface of said pad so that the diaphragm is not subjected to tensile stresses when the press is in the condition indicated in 11. Said diaphragm surface area is preferably greater than said pad surface area so that the diaphragm is under a slight compression when it `lies against the pad as shown in FlG. ll. This reduces the tensile forces on the diaphragm when the pressure is applied as indicated in FIGS. l2 and 13. The convex shape of the upper surface of the pad loa also minirnizes these tensile stresses.

T he sealing gasket iS3 is designed to prevent extrusion of the diaphragm 17a between the flange 94 a-nd the pad rim member 15a and has a normal cross-sectional area before mounting in the press at least equal to the maximum area of the space between said flange and said rim member. Since the materials of the gasket are incompressible, the gasket completely lls said space when maximum pressure is applied as indicated in FIGS. 12 and 13.

FGURES 19 and 20 show the gasket 153 in its normal unstressed condition prior to assembly between the pad rim member 15a and the plate 13a. The gasket comprises a exible elastic strip lili? of homogeneous incompressible rubber and upper and lower steel stnips 101 and lZ bonded to the rubber strip substantially through out its periphery.

The central portions 163 of the gasket are unreinforced and free to stretch so that the strips 191 and lilZ remain in engagement with the transverse portions 51 of the retaining ring 9 as the ring stretches longitudinally. The

11 operation of such gasket is described in United States Patent No. 3,006,306.

The rubber materials employed for the forming pads 16 and 15a and the diaphragms 17 and 17a may vary considerably. However, such materials should be flexi- Vble and elastic and should have substantial abrasion resistance and fatigue resistance. The forming pad and the throw pad may be made from high quality, abrasionresistant rubber having a durometer hardness in the neighborhood of about 50 to 70. The diaphragm 17a, however, must be made of a rubber which is not'subject to :swelling and degradation or otherwise damaged due to contact with the oil or other hydraulic fluid used in the pressure chamber. Such rubber should have maximum elongation and maximum flex-cracking resistance. The diaphragm is often made of neoprene when the hydraulic huid is an oil.

lt will be understood that the above description is by way of illustration rather than limitation and that, in accordance with the patent statutes, variations and modilications of the speciiic devices disclosed herein may be made without departing from the spirit of the invention.

This application is a division of copending United States application Serial No. 563,984 filed February 7, 1956, now Patent No. 3,006,306.

Having described our invention, we claim:

l. A hydraulic press comprising a frame having a pair of rigid members thereon, a deformable elastic rubber forming pad between said members, an inextensible rim vulcanized to said pad throughout the periphery thereof, means for supporting said rim in a tixed position between said rigid members, and means forming an expansible iluid pressure chamber between one of said rigid members and said pad to move the central portion of said pad toward the other of said rigid members, said central portion being materially thicker than the marginal portions of said pad and forming a generally convex surface facing said expansible chamber that extends between said marginal portions.

2. A hydraulic press comprising a rigid frame, a liexible elastic rubber forming pad, a rigid endless inextensible rim member vulcanized to the peripheral edge of said pad substantially throughout its periphery, means carried by said frame for supporting said rim member in a xed position, and means forming an expansible duid-receiving chamber adjacent one face of said rubber pad for applying pressure to said face, said pad being reduced in thickness at least about twenty percent throughout the periphery of the pad adjacent the margins of the pad to facilitate movement of the central portion of the pad and .ilexing of the marginal portions of the pad.

3. In a uid press having a rigid frame, an elastic rubber forming pad, a rigid rim member surrounding said pad and having an inner face vulcanized to the marginal edge of said pad, said member being mounted in a ixed position relative to said frame, said pad having an endless peripheral recess in the top face thereof adjacent said rim member that gradually decreases in depth at its opposite sides so that marginal portions of the pad adjacent the rim have a thickness at least about twenty percent less than the average thickness of the pad radially inwardly of the recess, and means for applying pressure to said pad including a thin exible elastic rubber diaphragm conforming to and covering the upper surface of said pad and engaging the bottom of said recess.

4. Apparatus as deiined in claim 3 wherein the pad increases in thiclmess radially outwardly of the recess and is bonded to the Yrim member or a distance parallel to the axis of the rim member materially greater than the minimum thickness of the pad and not substantially less than the average thickness of the pad radially inwardly of said recess.

5. ln a press of the character described herein, a generally rectangular homogeneous elastic rubber pad having a length of about eight to twelve feet, a width of about three to six feet, and an average thickness of about four to eight inches, an endless metal rim member having a substantially uniform height not substantially less than the average thickness of said pad and having an inner face vulcanized to the marginal edge of said pad throughout the width and perimeter thereof, said pad having an enlarged relatively wide central portion with opposite surfaces generally parallel, and a relatively narrow endless marginal recess in said pad adjacent said rim member that gradually decreases in depth at its opposite sides, said recess having sumcient depth so that the recessed portion of said pad has a minimum thickness that is about 20 to 40 percent less than theY thickness of said central portion, said central portion having a substantially uniform thickness at the center of the pad.

6. in a press of the character described herein, a generally rectangular homogeneous elastic rubber pad having a length of about eight to twelve feet, a width of about three to six feet, and an average thickness of about four to eight inches, an endless metal rim member with a substantially uniform height not substantially less than the average thickness of said pad and having an inner face vulcanized to the marginal edge of said pad throughout the width and perimeter thereof, said pad being substantially symmetrical with respect to a plane substantially midway between the opposite edges of said rim member and having a relatively wide substantially imperorate central portion with opposite surfaces generally parallel to said plane, and a relatively narrow endless marginal recess in said pad on each side of said plane and adjacent said rim member that gradually decreases in depth at its opposite sides toward said rim member and said central portion, said recess having a depth of at least about one-hair" inch so that the minimum thickness of the marginal portions of said pad is about twenty to forty percent less than the average thickness of the pad.

7. In a press of the character described, a generally rectangular substantially imperforate elastic rubber forming pad having a width of about three to six feet, a length .p to about twelve feet, and an average thickness of about four to eight inches, an endless rigid rim member having an inner face vulcanized to the marginal edge surface of said pad throughout the width and perimeter thereof, said pad having a relatively wide central body portion with an average thickness of about four to eight inches, an intermediate cuter portion surrounding said body portion that has a thickness at least one-half an inch less than that of said body portion, and a relatively narrow marginal portion extending around said outer portion adjacent said rim member that has a minimum thickness about twenty to forty percent less than the thickness of said body portion, said marginal portion gradually increasing in thickness toward the marginal edge surface of said pad member which has a height greater than that of said outer portion.

8. In a press of the character described herein, a generally rectangular homogeneous elastic rubber pad havinga length of about eight to twelve feet, a width of about three to six feet, and an average thickness of about four to eight inches, a rigid endless metal rim member with a substantially uniform height not substantially less than the average thickness of said pad and having an inner face vulcanized to the marginal edge of said pad throughout the width and perimeter thereof, said pad being substantially symmetrical with respect to a plane substantially midway between the opposite edges of said rim member and having a relatively wide central portion with opposite surfaces generally parallel to said plane, and a relatively narrow endless marginal recess in said pad on each side of said plane and adjacent said rim member that gradually decreases in depth at its opposite sides toward said rim member and said central portion, each said recess having a depth of at least about one-half inch and such that the minimum thickness of the marginal portions of said pad is about twenty to forty percentless 13 than the average thickness oi the pad, said central portion having a generally uniform thickness at the center of the pad.

9. In a press of the character described, an elastic rubber forming pad having a marginal portion of reduced thickness that increases in thickness toward the marginal edge of the pad, an endless metal rim member having an inner face vulcanized to said marginal edge throughout the length thereof, a rigid supporting member engaging the bottom of said rim member substantially throughout the perimeter thereof and having an upwardly projecting portion inwardly of the rim with a rounded convex surface for engaging the marginal portion of the pad substantially throughout the periphery thereof, and means above said rim member for holdinU the same against said supporting member.

l0. in a hydraulic press having a frame including a rigid supporting member and having a die carried by said member, a ilexible elastic rubber pad having a marginal portion with a smooth outer edge that extends around its periphery and having a thickened interior portion inwardly of said marginal portion that is movable toward and away from an article on said die, said marginal portion throughout its length decreasing in thickness from said outer edge toward said interior portion and said interior portion increasing in thickness from said marginal portion toward the center of the pad to form a convex surface on the side of the pad remote from said die, the portion of the pad surrounding said convex surface having a thickness that is about 2O to 40 percent less than the average thickness of said interior portion to facilitate exing of the rubber adjacent said marginal portion, a rigid rim member having an inner surface of a shape to lit the outer surface of said pad and bonded to said outer surface of said pad substantially throughout the periphery of the pad to hold said outer surface in a iixed position relative to said support'frg member and said die, said pad having a thickness at its outer edge not substantially less than the average thickness oi said interior portion, and duid motor means for moving said pad toward said die including means forming an expansible chamber adjacent the convex surface of said pad for applying pressure to the entire upper surface of said pad, said chamber being located above the peripheral edge portions of the pad adjacent said rim member to apply pressure to the pad adjacent said outer edge.

ll. A machine as defined in claim l wherein said fluid motor means includes a rigid frame member generally parallel to and spaced from said pad and a flexible elastic rubber diaphragm having a central portion that conforms to the shape of said pad substantially throughout the length and width of said pad and a rounded marginal portion that extends from said central portion away from said pad and toward its marginal edge, the radially inner portions of the diaphragm adjacent said marginal edge being clamped to said frame member to prevent leakage of tluid from said chamber between said frame member and said diaphragm.

l2. A hydraulic press as defined in claim l0 wherein said uid motor means includes a tlexible elastic rubber diaphragm covering the entire pad and extending substanti-ally to the outer peripheral surface of said pad for applying downward pressure to the entire upper surface of the pad.

13. In combination, a fluid press having a rigid frame, a horizontal elastic rubber forming pad having a top face, a rigid rim member surrounding said pad and having an inner face vulcanized to the marginal edge of said pad, said member being mounted in a fixed position relative to said frame, said pad having an endless marginal recess in the top face thereof adjacent said rim member that gradually decreases in depth at its opposite sides so that marginal portions of the pad adjacent the rim have a thickness from about twenty to forty percent less than the average thickness Of the pad radially inwardly of the ldrecess, said pad gradually increasing in thickness radially outwardly of the recess and being bonded to the rim member for a distance parallel to the axis of the rim member materially greater than the minimum thickness of the pad and not substantially less than the average thickness of the pad radially inwardly of said recess.

14. A hydraulic press having a retainer ring with internal vertical surfaces providing a substantially rectangular enclosure, a forming pad of elastic rubber extending the full length and width of said enclosure, a rigid rim member having an inner face vulcanized to the marginal face of said forming pad and an outer face engaging said vertical surfaces substantially throughout the periphery of said enclosure, means for holding said rirn member in a fixed position in said enclosure, said pad having a marginal portion providing an endless recess in each of the top and bottom faces thereof adjacent said rim member, said pad having a thickness at its marginal face not substantially less than the average thickness of the pad inwardly of said marginal portion and a minimum thickness at said recess about twenty to forty percent less than sai average thickness, the thickness of the pad gradually increasing in an axial direction away from the central portion of each recess, and means forming an expansible chamber above said pad including a thin elastic rubber diaphragm normally conforming to and covering the marginal recess in the top face of the pad and engaging said rim member.

l5. In a press of the character described, a horilontal generally rectangular elastic rubber forming pad having a width oi about three to six feet, a length up to about twelve feet, and an average thickness of about four to eight inches, an endless rigid rim member having an inner face vulcanized to the marginal edge surface of said pad throughout the width and perimeter thereof, said pad having a relatively wide continuous central body portion with a generally uniform thickness of about four to eight inches, an intermediate outer portion ot smaller area surrounding said body portion and having a thickness at least one-half inch less than that of said body portion, and a relatively narrow marginal portion with a horizontal width less than that of said outer portion adjacent said rim member and extending around said outer portion, said marginal portion having a marginal edge surface with a height greater than that of said intermediate outer portion and having a minimum thickness about twenty to forty percent less than the thickness of said body portion, said marginal portion gradually increasing in thickness toward the marginal edge surface of said pad member to provide marginal top and bottom surfaces of rounded cross section.

16. ln a press of the character described, in combination, a horizontal generally rectangular elastic rubber forming pad having top and bottom faces and having a width of about three to six feet, a length up to about twelve feet, and an average thickness of about four to eight inches, an endless rigid rim member having an inner face vulvanized to the marginal edge surface of said pad throughout the width and perimeter thereof, said pad having a central body portion with a generally uniform thickness of about four to eight inches, an outer portion of smaller area surrounding said body portion and having a thickness at least one-half an inch less than that of said body portion, and a marginal portion with a horizontal width less than that of said outer portion adjacent said rim member and extending around said outer portion, said marginal portion having a marginal edge surface with a height greater than that of said outer portion and having a minimum thickness about twenty to forty percent less than the thickness of said body portion, said marginal portion gradually increasing in thickness toward the marginal edge surface of said pad member, the lower face of said pad having an endless marginal recess of rounded cross section adjacent said rim member that gradually decreases in thickness in directions away from the central portion yof the recess, a rigid supporting member engaging the bottom of said rim member substantially throughout the perimeter thereof and having an upwardly projecting portion inwardly of the rim with a rounded convex upper surface for engaging the central portion of said recess substantially throughout the perimeter thereof, said pad being unsupported and out of contact with said supporting member inwardly of said convex surface, and means above said rim member for holding the same against said supporting member.

17. A hydraulic press having a retainer ring with internal vertical surfaces providing a substantially rectangu-V lar enclosure, a forming pad of elastic rubber extending the full length and width of said enclosure, a rigid rim member having an inner face vulcanized to the marginal edge face of said forming pad and an outer face engaging said vertical surfaces substantially throughout the periph# ery of said enclosure, means for holding said rim member in a fixed position in said enclosure, said pad having a marginal portion adjacent said rim member, a central body portion of a thickness greater than that of said marginal portion, and an intermediate outer portion connecting said body portion and said marginal portion and having a thickness not substantially greater than the thickness of said marginal portion at the marginal face, said outer portion having a thickness about ten to twenty-five percent less than the thickness of said central portion, said marginal portion having a minimum thickness inwardly of the marginal edge face that is about v`twenty. toforty percent less than that of said ycentral portion, said pad having an endless marginal recess below said marginal portion and adjacent said rim member that gradually decreases in depth in directions away from the central portion of the recess, and means forming an expansiblechamber above said pad including a thin elastic rubber diaphragm normally conforming to and coveringsaid marginal portion and engaging said rim member.

18. Rubber forming means for a hydraulic press having 16 a rigid frame with internal vertical surfaces providing a substantially` rectangular enclosure of a size to receive said forming means, narrow clamping means at the margin of said enclosure, and a thin elastic rubber diaphragm inwardly of said clamping means extending substantially the full width and length of said enclosure, said forming means comprising: a horizontal generally rectangular elastic rubber pad having a length of at least eight feet, a width of at least three feet, and an average thickness of at least four inches, and an endless metal rim member having a substantially uniform height not substantially less than the average thickness of said pad and having an inner vertical face vulcanized to the marginal edge of said pad throughout the width and perimeter thereof, said rim member being of a size to fit between parts of said clamping means outwardly of said pad and to engage the vertical walls forming said enclosure, said pad having an upper surface with a width and length no greater than that of said diaphragm for receiving pressure from said diaphragm and having an enlarged relatively wide central portion which has a generally uniform thickness at its enter and which has its top and bottom surfaces substantially parallel, said pad having a relatively narrow continuous recess contiguous to said rim member that gradually decreases in depth at its opposite sides, said recess extending around the entire periphery and having suiicient depth so that the recessed portion of the pad has a minimum thickness at least 20 percent less than the thickness of said central portion.

References Cited in the le of this patent UNITED STATES PATENTS 1,885,457 Lord et al. Nov. 1, 1932 2,741,205 Paulton Apr. 10, 1956 2,771,850 Wheelon Nov. 27, 1956 2,854,940 Bates Oct. 7, 1958 2,962,994 Wheelon Dec. 6, 1960 FOREIGN PATENTS 510,090 Belgium Sept. 1l, 1953 

1. A HYDRAULIC PRESS COMPRISING A FRAME HAVING A PAIR OF RIGID MEMBERS THEREON, A DEFORMABLE ELASTIC RUBBER FORMING PAD BETWEEN SAID MEMBERS, AN INEXTENSIBLE RIM VULCANIZED TO SAID PAD THROUGHOUT THE PERIPHERY THEREOF, MEANS FOR SUPPORTING SAID RIM IN A FIXED POSITION BETWEEN SAID RIGID MEMBERS, AND MEANS FORMING AN EXPANSIBLE FLUID PRESSURE CHAMBER BETWEEN ONE OF SAID RIGID MEMBERS AND SAID PAD TO MOVE THE CENTRAL PORTION OF SAID PAD TOWARD THE OTHER OF SAID RIGID MEMBERS, SAID CENTRAL PORTION BEING MATERIALLY THICKER THAN THE MARGINAL PORTIONS OF SAID PAD AND FORMING A GENERALLY CONVEX SURFACE FACING SAID EXPANSIBLE CHAMBER THAT EXTENDS BETWEEN SAID MARGINAL PORTIONS. 